1. Field of the Invention
The present invention relates to a method for adjusting an amount of discharge to equalize amounts of discharges from a plurality of liquid discharge units, an ink jet apparatus for discharging ink droplets from the ink discharge nozzles, and a method for driving an ink jet head used for the ink jet apparatus. More particularly, the invention relates to a method for driving an ink jet head provided with a plurality of heat generating elements for air bubble creation, each in the ink liquid path corresponding to each of the ink discharge nozzles, for discharging ink by the creation of air bubbles by the application of heat. The invention also relates to an ink jet apparatus using such ink jet head.
2. Related Background Art
The ink jet apparatus is well known as one mode of a recording apparatus, such as a printer, a copying machine. Of the apparatuses, the ink jet recording apparatus which uses a discharge method, whereby air bubbles are created by causing thermal energy to act upon ink or other liquid, and to discharge ink from the ink discharge ports by a discharge force following the creation of air bubbles, has been getting more popular rapidly in recent years. As another use of the ink jet apparatus using a discharge method of this kind, an ink jet textile printing apparatus is also well known. This apparatus prints specific patterns, designs, synthetic images, or the like on cloths.
For the conventional ink jet apparatuses including the ink jet textile printing apparatus, there are some cases where the amount of discharge may vary due to changes in temperature, or when a plurality of ink discharge nozzles are used for discharging ink, the amount of discharge varies between discharge nozzles, and an uneven recording (an uneven printing) may take place. Several methods have been proposed and practically in use for the suppression of the uneven recording that may be caused by changes in temperature and the variation of discharge amount between discharge nozzles.
Now, among ink jet recording apparatuses, the one, which is provided with heat generating elements for the creation of air bubbles by means of heat generated by such elements, and which discharges ink by such creation of air bubbles, tends to allow part of thermal energy applied to the creation of air bubbles to cause the temperature of the ink jet head (discharge head) to rise. As a result, the amount of discharge may vary due to the resultant rise of environmental temperature, and the temperature of the head itself as well. This variation of discharge amount is brought about by changes in ink viscosity, and also, changes in the facility of air bubble creation caused by changes in the temperature of ink. Consequently, for example, the head temperature increases as the recording operation progresses, thus leading to the varied amount of discharges. Then, a problem is encountered that the quality of images changes. In this respect, therefore, a proposal has been made to enable an ink jet apparatus of the kind to control not only the discharge amounts by adjusting over all temperatures, but also, to devise a method for utilizing thermal energy more effectively for the creation of air bubbles.
When electrothermal transducing elements are used as heat generating elements, the width of applied pulses is changed for the creation of air bubbles or before the application of main pulses for the air bubble creation, a pre-pulse is applied in the temporal width that is not intensive enough to create any air bubbles, and then, the discharge amount is controlled by changing the width of the pre-pulse, and the quiescent time between the pre-pulse and the main pulse. Also, a proposal has been made to adopt a control of the discharge amount of the kind for the suppression of the variation per discharge nozzle.
However, in accordance with the conventional method for controlling the discharge amount described above, the changeable range of the discharge amount is not large enough, and if the rate of printing duty is continuously high, the temperature of ink jet head is caused to rise considerably. Therefore, it becomes necessary to secure a sufficient margin for the discharge nozzles to execute control to suppress the variation of discharge amount. This marginal arrangement automatically restricts the effective use of those proposed methods, and even makes it difficult in some cases to control the variation of discharge amount caused by changes in temperature and the variation between discharge nozzles sufficiently.
It is an object of the present invention to provide a new method for adjusting an amount of discharge to equalize the discharge amounts between a plurality of liquid discharge units, and at the same time, to provide an ink jet apparatus provided with electrothermal transducing elements as heat generating elements to create air bubbles for discharging, which is capable of securing a sufficiently wide controllable range for controlling the discharge amount constantly even when one or both of variations of the discharge amount are great due to the variation of discharge amount caused by changes in temperature of ink and head or caused by the individual difference of a particular discharge nozzle or the nozzle group. It is also the object of the invention to provide a method for driving the ink jet head for such ink jet apparatus.
The method for adjusting an amount of discharge of the present invention mainly comprises the step of adjusting the amount of liquid between each of liquid discharge units for discharging the liquid by driving a plurality of electrothermal transducing elements by use of a plurality of liquid discharge units, which are arranged corresponding to each liquid path to create air bubbles for discharging the liquid, and at the same time, arranged to be capable of being driven individually. This method is to control the discharge amount of liquid between each of the liquid discharge units by variably controlling the starting time of driving signal applied to each of the electrothermal transducing elements in each discharge unit between each of the liquid discharge units for suppressing the variation of discharge amount of liquid between each of the liquid discharge units.
The method for driving an ink jet head of the present invention mainly comprises a step of driving a plurality of electrothermal transducing elements together by providing a plurality of discharge nozzles having a plurality of electrothermal transducing elements arranged to create air bubbles for discharging ink, and at the same time, arranged to be capable of being driven individually. This method is provided with a first control to apply driving signals, each formed by the main pulse to generate thermal energy for the creation of air bubbles; the pre-pulse preceding the main pulse for heating but not intensive enough to create any air bubbles; and the quiescent time between the main pulse and the pre-pulse, such driving signals being applied to the plural electrothermal transducing elements in order to change each driving signal itself. This method is also provided with a second control to shift the application timing of the main pulse to be applied to the plural electrothermal transducing elements in the discharge nozzles, and then, to suppress the variation of discharge amount caused by changes in the temperature of ink by means of either one of the first and second controls, as well as to suppress the variation of discharge amount between the discharge nozzles by means of the other one of the first control and the second control.
Also, for such method for driving an ink jet head, either one of the first control and the second control is performed when the temperature detected from the head is within a range up to a specific target temperature in order to suppress the variation of discharge amount caused by changes in temperature, and the other one of the first control and the second control is performed to suppress the variation of discharge amount caused by the individual difference between discharge nozzles or between discharge nozzle groups. When the detected temperature exceeds the target temperature, the first and second controls are combined to suppress the variation of discharge amount caused by changes in the temperature of ink.
Or with the provision of plural discharge nozzles having a plurality of electrothermal transducing elements arranged to create air bubbles for discharging ink, and at the same time, arranged to be capable of being driven individually, it is made possible for a method for driving an ink jet head to drive such plurality of electrothermal transducing elements together to discharge ink, and then, to suppress the variation of liquid discharge amount between each of the liquid discharge units by variably controlling the starting time of application of signals to each of the electrothermal transducing elements in the nozzles for creating air bubbles.
Also, the ink jet apparatus of the present invention mainly comprises an ink jet head provided with plural nozzles having a plurality of electrothermal transducing elements arranged to create air bubbles for discharging ink, and at the same time, arranged to be capable of being driven individually, and arranged to discharge ink by driving such plurality of electrothermal transducing elements together. This ink jet apparatus comprises temperature detection means for detecting temperatures of the ink jet head; data storing means for storing correction data to correct the variation of discharge amount between discharge nozzles or between discharge nozzle groups; driving means for applying driving signals, each formed by the main pulse to enable each of the electrothermal transducing elements to generate thermal energy per discharge nozzle for the creation of air bubbles, the pre-pulse preceding the main pulse for heating but not intensive enough to create any air bubbles, and the quiescent time between the main pulse and the pre-pulse, in accordance with recording data; and controlling means for performing a first control to change the conditions of the pre-pulse application in accordance with the data stored in the data storing means, and also, performing a second control to shift the application timing of the main pulses between electrothermal transducing elements per discharge nozzle.
Or an ink jet apparatus comprises an ink jet head provided with plural nozzles having a plurality of electrothermal transducing elements arranged to create air bubbles for discharging ink, and at the same time, arranged to be capable of being driven individually, and arranged to discharge ink by driving such plurality of electrothermal transducing elements together. This ink jet apparatus comprises temperature detection means for detecting temperatures of the ink jet head; data storing means for storing correction data to correct the variation of discharge amount between discharge nozzles or between discharge nozzle groups; driving means for applying driving signals to enable each of the electrothermal transducing elements to generate thermal energy for the creation of air bubbles per discharge nozzle in accordance with recording data; and controlling means for performing a control to shift the application timing of the driving signal between the electrothermal transducing elements per discharge nozzle or discharge nozzle group in accordance with the result of detection of the temperature detection means, and the data stored in the data storing means as well.
With the provision of a plurality of electrothermal transducing elements for the creation of air bubbles in each liquid path for each nozzle that comprises the discharge port and the liquid path conductively connected therewith (typically, an ink path), it is possible to shift the timing of the air bubble creation on each of the electrothermal transducing elements by shifting the application timing of the main pulses to be applied to these electrothermal transducing elements for the creation of air bubbles, that is, at least one kind of time differential xcfx84 is set with respect to the application timing of the main pulses to such plurality of electrothermal transducing elements. In this way, the timing of air bubble creation on each of the electrothermal transducing elements is allowed to shift, hence making it possible to change the discharge amount of each discharge port. More specifically, if the main pulses are applied at a time (that is, the time differential xcfx84 is set at 0), the discharge amount becomes maximum as described later, and the larger the time differential xcfx84 when applying the main pulses to each of the electrothermal transducing elements, the more is the discharge amount reduced. Here, for the present invention, using this time differential xcfx84 it is intended to control the discharge amount for the stabilization thereof. In this way, the discharge amounts are equalized between a plurality of liquid discharge units or between discharge nozzles.
Particularly, for the discharge amount control with respect to an ink jet head, the pre-pulse control and the control by means of the time differential xcfx84 are combined for use, and typically, one of these controls is applied to suppressing the variation of discharge amount caused by changes in the temperature of ink, and the other one of them is applied to suppressing the variation of discharge amount caused by the individual difference between discharge nozzles (discharge nozzle groups). In this way, even if either one or both of the variation of ink temperature and the individual difference between discharge nozzles (discharge nozzle groups) are so large that a sufficiently controllable range cannot be obtained just by either one of them, it becomes possible to secure a wide controllable range by the combined use of both of them.